The present invention relates to a device for controlling a movable member which is applicable for controlling a stop position of a movable lens of a focal length changeable type camera, and also applicable for controlling a lens position of a focal length changeable type camera of rear converter type.
Widely has been used a camera carrying a taking lens capable of changing the focal length. In such a focal length changeable lens camera, it is usual to move a movable lens by use of an internally equipped motor in response to switching operation. Specifically, a lens position detection switch detects that the movable lens reaches a specified stop position (i.e. end position) of a telephoto focal length state, standard focal length state, or wide angle focal length state. Subsequently, the internally equipped motor is suspended or driven in response to outputs of the switch.
In such a focal length changeable lens camera, also, it has been required to change the focal length in prompt response to photography purposes. Therefore, the movable lens is moved at high speed so that a rapid change in focal length is attainable. It could be seen that even if the movable lens has a small weight, the movable lens has a considerably great momentum. Accordingly, even when the movable lens is stopped immediately after the lens position detection switch detects that the lens reaches the specified stop position, there is a likelihood that the movable lens rebounds at the specified stop position and stops at a position before the specified stop position. Consequently, there is a likelihood that a designed photography performance can not be obtained due to the positional error of the movable lens.
Also, in such a focal length changeable lens camera, changing the focal length changes the projection amount of the lens. In a focal length changeable type camera of rear converter type when the focal lens is set in the telephoto focal length state, the projection amount of the lens is considerably great. This is because the lens must be projected corresponding to an amount in which a rear converter lens is introduced behind the lens retracted. When a loaded film is not wound by the tail portion, it is usual that the lens is required to be set not only in the standard focal length state (or wide angle focal length state), i.e., a retracted state but also in the telephoto focal length state, i.e., a projected state. When the film is wound by the tail portion, there are few occasions that the lens is required to be set at the projected state. Also, when the wound film is rewound, there are few occasions that the lens is required to be set at the projected state. It could be seen that a considerably projected lens lowers the portability of the camera. Accordingly, it is desired that when the camera is not put into work and is carried, the lens be set in the retracted state.
As mentioned above, in such focal length changeable lens cameras, it is usual to move the movable lens by use of an internally equipped motor in response to switching operation. Furthermore, it is usual in such a camera that all the switches of the camera are not allowed to operate during the time from start of the film rewinding operation to opening of the rear cover. Accordingly, there is a disadvantage that when the film rewinding operation is started with the lens being set in the projected state, the lens can not be set from the projected state to the retracted state until the film rewinding operation is completed and the rear cover is opened. Even if the lens is made changeable from the projected state to the retracted state even after starting of the rewinding operation, there is another disadvantage that the lens moves uselessly in spite of the state that photography is unexecutable.